Season of birth: issues, approaches and findings for autism
Bolton, P.; Pickles, A.; Harrington, R.; Macdonald, H.; Rutter, M.
Journal of Child Psychology and Psychiatry and Allied Disciplines 33(3): 509-530
1992
ISSN/ISBN: 0021-9630 PMID: 1577896 DOI: 10.1111/j.1469-7610.1992.tb00888.xDocument Number: 321346
Rates of birth in the general population show seasonal fluctuations for reasons that are ill understood. Variations from these general population pattenrs have been reported for several psychiatric conditions and used as the basis for aetiological hypothezses. In this paper, the evidence for alterations in the expected seasonal fluctuation in birth dates of autistic people is evaluated. A national sample of 1435 autistic individuals and a clinic sample of 196 subjects are compared to general population figures and to 121 sibling controls. Compared with the general population, the national sample showed significant deviations from the expected rate of birth by month. In the clinic sample, differences from the anticipated monthly pattern were only evident when this sample was compared to the sibling controls. A variety of models for seasonal trends, including year quarters, temperature and sine wave forms, were fitted to these variation but no consistent picture emerged.